\begin{tikzpicture}
    \tkzDefPoints{0/0/O, -3/-0.4/P}
    \tkzDefPoint(-20:1.5){A}
    \tkzDefPoint(80:1.5){C}
    \tkzInterLC[common=A](P,A)(O,A)  \tkzGetFirstPoint{B}
    \tkzInterLC[common=C](P,C)(O,A)  \tkzGetFirstPoint{D}

    \tkzDefMidPoint(O,P)  \tkzGetPoint{Q}
    \tkzInterCC(O,A)(Q,P)  \tkzGetFirstPoint{T}

    \tkzDrawCircle[thick](O,A)
    \tkzDrawPoint(O)
    \tkzDrawLine[add=0 and 0.4](P,T)
    \tkzDrawSegments(P,A  P,C)
    \tkzDrawSegments[dashed](T,A  T,B)
    \extkzLabelAngel[0.8](B,T,P){$1$}

    \tkzLabelPoints[above](O)
    \tkzLabelPoints[right](A)
    \tkzLabelPoints[above, xshift=.5em](B)
    \tkzLabelPoints[above](C)
    \tkzLabelPoints[above left](D)
    \tkzLabelPoints[left](P)
    \tkzLabelPoints[below](T)
\end{tikzpicture}

